Deep Vein Thrombosis: A Hidden Risk of Being a Healthy, Active Cyclist

Endurance athletes’ lifestyle may make them more susceptible to potentially fatal DVT. Here are the risk factors and symptoms to watch out for.

Vicki Barclay was feeling off. The PhD, 34, a research scientist and mountain bike racer for Stan’s Notubes Elite Women’s team recalls that “for about a week I just didn’t feel right. I felt like I had bad indigestion and discomfort on my left side.” It never occurred to her that it could be a serious blood clotting condition, called Deep Vein Thrombosis; instead, she chalked it up to previous injuries, travel and stress. But then, things got much worse. “I raced a cyclocross race that Saturday and had a pounding headache. I tried to ride the next day and was insanely breathless. Then I drove ten hours to do a ride I’d planned in Pisgah, North Carolina, but I was so weak I couldn’t even get on my bike. I ended up blacking out and going to the hospital.”

The diagnosis was multiple blood clots (pulmonary emboli) in her lungs and a large clot (deep vein thrombosis) in her right leg. Barclay was admitted to the hospital, put on blood thinners and forbidden from mountain biking for the foreseeable future. “I can’t believe it happened to me. I should recover, albeit with a few bits of dead lung, but I went from easily completing multiple workouts a day to struggling to walk without help. The lesson I learned from this experience is not to always push through pain; sometimes stopping and listening to your body can save your life.”

So can knowledge of your risks, adds Barclay, which she wants more riders—especially women—to have.

DVT Risk Factors

Your genes. About 5 to 8 percent of the population are born with a genetic predisposition for blood clotting disorders. This alone won’t necessarily lead to DVT or pulmonary embolism, though, unless triggered by another risk factor.

Injuries. Damage to a vein caused by bone fractures, severe muscle injury, and/or surgery raise your risk—a good thing to keep in mind should you have a bad crash.

Slow blood flow. Pay close attention to this one! If you’re well-conditioned, you likely already have a low resting heart rate. So when you’re especially immobile or sedentary, your calf muscles (which are known in medical circles as your second heart) don’t contract to assist circulation and blood can pool in your extremities, raising your risk. Sitting in a cramped plane for a long flight is an obvious one, but research shows that more people are being admitted to the hospital for DVT because of long hours sitting at their desk jobs.

Hormones. Estrogen via birth control and hormone replacement therapy can increase your blood’s clotting ability, as can pregnancy, though DVT is by no means a single-gender issue. Bicycling’s own gear editor Matt Phillips was struck with a DVT in early 2014, and ended up on blood thinners for four months. “It was likely a combination of dehydration and travel. I did a hard Grand Fondo in Italy, got on a plane and flew home. Did another long airline trip a few days later and ended up with nagging pain in my soleus that I couldn’t stretch or massage out,” says Phillips, who sought urgent care after about 30 days when it still hadn’t cleared up. “Luckily it didn’t break loose and become a pulmonary or aortic embolism,” he says.

Hindsight is 20/20

Barclay was on birth control pills, and eight weeks prior to her hospitalization, she’d crashed in a pro XC race and cracked four ribs. Six weeks after breaking her ribs, she flew to Utah and rode with her teammates at altitude, which is naturally dehydrating. Finally, as a well-trained endurance athlete, Barclay has a low resting heart rate.

“She had the perfect storm—a tsunami, really—of risk factors,” says exercise physiologist Stacy Sims, PhD, author of ROAR, How to Match Your Food and Fitness to Your Unique Female Physiology for Optimum Performance, Great Health, and a Strong, Lean Body for Life. “Because she’s a healthy, young, athletic woman, she’s used to pushing through discomfort and pain and not inclined to think that something is wrong with her even when she’s getting warning signs.”

That can have severe consequences. One of Sims’ longtime Ironman acquaintances also recently developed DVT and was put on Warfarin (a blood thinner) to clear it. Problem was that she was allergic to the medicine and ended up with sepsis below the clot in her lower leg. She ultimately had to have part of her leg amputated.

DVT Signs and Symptoms

As a cyclist, you likely have your share of aches and pains now and then, so it’s easy to ignore a little nagging ache. But you shouldn’t ignore these, especially if you have risk factors for DVT. Symptoms and signs of DVT may include the following and should be checked by your doctor.

Also be aware of signs of pulmonary embolism, which can occur without any signs of DVT (some DVT are “silent,” meaning they have no symptoms). Signs and symptoms of pulmonary embolism include the following and are considered a medical emergency—get help immediately.

Difficulty breathing

Chest pain or discomfort, generally worsens with deep breathing.

Coughing up blood

Racing heartbeat

Lightheadedness and/or fainting

An Ounce of Prevention…

So now you’ve got phantom calf pain and you’re convinced you can’t breathe, right? Believe us, we get it. To keep it in perspective, the actual risk for VTE (venous thromboembolism, such as DVT and pulmonary embolism) is still relatively low, with an estimated annual incidence of about 0.1 percent in the general population. However, even one incident can cause long-term complications, such as swelling and pain in the affected limb—and a pulmonary embolism can be fatal. So it’s vital to know how to lower your risk, what to watch for, and what to do should symptoms arise.

Rock the socks. We can debate the usefulness of compression socks for recovery and performance. But, they may help to prevent DVT because they apply gentle pressure across the foot, ankle and calf to promote circulation and prevent swelling. Wear a pair during long flights, especially if you’re flying after a race or big event where you might have elevated risk from dehydration and exertion. (Some experts, however, caution against using calf sleeves, as they can actually lead to swelling in the ankles and feet.)

Move your muscles. Get up and move as often as possible—at least every couple of hours, whether you’re on a long flight or at the office. While seated, exercise your calf muscles by doing toe and heel raises. “If you train, then sit all day or sit all day and then train, you need to make a conscious effort to stand up and walk around when you can throughout the day,” says Sims. “Circulation is your friend!”

Stay hydrated. Travel with a bottle and a sleeve of your favorite hydration drink, so you can fill up and stay hydrated during the flight and as you travel. Be sure to rehydrate after races and events, especially if you’re getting right into a car or plane to make the trip home afterward.

Reconsider your contraception. If you are on a combined oral contraceptive pill, the patch, or the ring (all of which contain estrogen), consider switching to an IUD or progestin-only mini pill, suggests Sims. “Estrogen increases clotting factors, and the synthetic estrogen in oral contraceptives more than triples the risk for DVT,” she says.

Pop some baby aspirin. If you’re flying after a race, event and/or bike trip, take a baby aspirin (81 mg low dose) for five days prior to travel as a low-dose blood thinner. “This is particularly important for women during their high hormone phase before their period or if they are taking oral contraception that contains estrogen,” says Sims.